Methods and apparatus for treating infarcted regions of tissue following acute myocardial infarction

ABSTRACT

Apparatus and methods are provided for treating an infarcted region of myocardium following acute myocardial infarction by reducing the rate of blood flow through infarcted region, and then injecting a solution containing stem cells, endothelial progenitor cells or mediators of stem cell mobilization, migration and attachment into the effected region so that the stem cells become embedded therein and promote tissue regeneration. In a first embodiment, delivery of the stem cells, endothelial progenitor cells or mediators of stem cell mobilization, migration and attachment is accomplished using a catheter that relies upon antegrade flow through the coronary artery and a flow control catheter placed in the coronary sinus. In an alternative embodiment, the delivery catheter delivers the stem cells in a retrograde manner through the coronary sinus, and the delivery catheter further comprises an occlusion balloon for controlling outflow through the coronary sinus ostium.

FIELD OF THE INVENTION

The present invention relates to apparatus and methods for injecting andembedding autologous body material, including stem cells, endothelialprogenitor cells or mediators of stem cell mobilization, migration andattachment into an infarcted region of the patient's heart.

BACKGROUND OF THE INVENTION

Myocardial infarction is caused by an abrupt occlusion of a coronaryartery resulting in interruption of circulation to the affected muscle.It is now known that most myocardial infarctions occur when a blockagein the coronary artery ulcerates creating a milieu for clot formation.The cause of this change in plaque morphology (ulceration) is unclearbut may be related to an inflammatory cascade or some other yet to bedetermined “trigger”. The term now used to describe this transition incoronary lesion morphology preceding myocardial infarction is“vulnerable plaque”. Rarely coronary artery occlusion may be caused byclot from a remote location (paradoxical embolic event from a deepvenous thrombosis or migration of clot from an left ventricularthrombosis). Even less common is embolic septic emboli from valveinfections or spontaneous coronary dissection

In either of the foregoing scenarios, once the blockage occurs, theportions of the heart muscle nourished by the effected artery becomesischemic and cell death or “necrosis” begins within minutes. If theblockage can be opened quickly, e.g., generally in less than 15 minutes,the infarcted region may continue to perform without degraded function.Accordingly, great urgency is required in resolving a blockage once itis formed.

As is well-known, most tissue in the human body originates fromundifferentiated cells known as stem cells. These fundamental buildingblocks differentiate into specific target parenchymal tissue based onhormonal and other signals. Scientific evidence suggests that stemscells or endothelial progenitor cells injected into a target tissue willdifferentiate into the cell line of that specific tissue. This featureis of particular interest in treating conditions involving organs thatcannot regenerate, such as the heart.

It has been postulated that it may be possible to improve function of aninfarcted region of heart muscle by injecting stem cells or endothelialprogenitor cells into the effected region as soon as the blockage isresolved. Unfortunately, conventional methods of separating stem cellsfrom autologous material, such as bone marrow, typically require severalhours of laboratory processing and culturing—far too long to provideeffective near-term treatment for an acute myocardial infarction.

Since stem cells and endothelial progenitor cells have been observed inthe circulation, it also may be beneficial to inject mediators of stemcell mobilization, migration and attachment. For example,Granulocyte-stimulating factor (GSF) and stem cell factor (SCF) mobilizestem cells from the bone marrow may be introduced into circulation.Vascular endothelial growth factor (VEGF) and stromal-cell derivedfactor-1 (SDF-1) causes release of homing factors that may bringcirculating progenitor cells to the infracted myocardium to assist inrepair.

In addition, it has been observed that blood vessels within ischemictissue tend to dilate. Accordingly, even where direct injection of stemcells into the cardiac vasculature is possible, such a process would beimpractical after the blockage has been opened, as the dilatedmyocardial blood vessels would permit the injected stem cells to beswept through the vessels so quickly that only a small percentage of thestem cells could embed in the tissue.

In view of the aforementioned limitations of previously-known systemsand methods, it would be desirable to provide apparatus and methods fortreating myocardial infarction by controlling the rate of blood flowthrough the vessels of infarcted tissue during introduction of stemcells into the region.

It would further be desirable to provide apparatus and methods fortreating myocardial infarction by occluding the coronary sinus, and theninjecting stem cells into a coronary artery.

It also would be desirable to provide apparatus and methods for treatingmyocardial infarction by inducing retrograde blood flow within thecoronary sinus, and then injecting stems cells into the coronary sinus.

It still further would be desirable to provide apparatus and methods fortreating myocardial infarction using direct injections of autologousmaterial, e.g., such as bone marrow aspirants, into the cardiacvasculature to promote tissue regeneration in an infarcted region of themyocardium.

It also would be desirable to provide apparatus and methods for inducingretrograde blood flow within the coronary venous vasculature that do notrequire an external power source, but instead may be driven bynaturally-occurring pressure gradients within the patient's body.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide apparatus and methods for treating myocardial infarction bycontrolling the rate of blood flow through the vessels of infarctedtissue during introduction of stem cells, endothelial progenitor cellsor mediators of stem cell mobilization, migration and attachment intothe region.

It is another object of this invention to provide apparatus and methodsfor treating myocardial infarction by occluding the coronary sinus, andthen injecting stem cells, endothelial progenitor cells or mediators ofstem cell mobilization, migration and attachment into a coronary artery.

It is also an object of the present invention to provide apparatus andmethods for treating myocardial infarction by inducing retrograde bloodflow within the coronary sinus, and then injecting stems cells,endothelial progenitor cells or mediators of stem cell mobilization,migration and attachment into the coronary sinus.

It is a further of this invention to provide apparatus and methods fortreating myocardial infarction using direct injections of autologousmaterial, e.g., such as bone marrow aspirants, into the cardiacvasculature to promote tissue regeneration in an infarcted region of themyocardium.

It is still another object of this invention to provide methods andapparatus for inducing retrograde blood flow within the coronary venousvasculature that do not require an external power source, but insteadmay be driven by naturally-occurring pressure gradients within thepatient's body.

These and other objects of the invention are accomplished by providingapparatus and methods for treating acute myocardial infarction (“acuteMI”) using injections of autologous material to promote tissueregeneration. As noted above, during acute MI the permeability of theinfarcted zone increases and capillaries and vessels within the zonedilate. After the blockage is opened, it may be impractical to injectstem cells or other materials into the region because blood flow throughthe dilated vessels would sweep away injected stem cells so quickly thatonly a small percentage of the stem cells would embed in the region.

In accordance with the principles of the present invention, apparatusand methods are provided to enhance the residence time of stem cellsinjected in the effected region, comprising a delivery catheter and aballoon for partially or completely occluding outflow through thecoronary sinus. In a first embodiment, the delivery catheter deliversthe stem cells via antegrade flow, while a flow control catheter partlyor completely blocks outflow through the coronary sinus ostium. In analternative embodiment, the stem cells are delivered in a retrogrademanner through the coronary sinus using an arterial shunt.

In a first embodiment, following angioplasty to open the blockage, adelivery catheter is inserted via a femoral artery into a desiredcoronary artery, such as the left anterior descending coronary artery.The delivery catheter is used to deliver a solution of containingautologous or donor stem cells, endothelial progenitor cells ormediators of stem cell mobilization, migration and attachment into theartery. The flow control catheter comprises a balloon-tipped catheterconfigured to occlude the coronary sinus, so that outflow through thecoronary sinus ostium is controlled to a desired level during deliveryof the material from the delivery catheter. In this manner, passage ofblood through the infarcted myocardium may be substantially slowed orarrested, thereby increasing stem cell residence time and enhancinguptake in the affected region.

Additionally, the delivery catheter may include an occlusion balloonconfigured to be disposed just inside the ostium of the target coronaryartery. Following deflation of the occlusion balloon of the flow controlcatheter, blood within the coronary sinus may be aspirated through thedelivery catheter, thereby ensuring that any non-embedded material doesnot embolize. After the stem cells embed in the infarcted zone, and theresidual material is aspirated from the artery, both the deliverycatheter and the flow control catheter are removed, thereby restoringantegrade blood flow.

In an alternative embodiment, the delivery catheter comprises an outletend that is disposed via a femoral vein into the coronary sinus. Thedelivery catheter is coupled to an arterial line that is placed in thepatient's femoral artery. Due to naturally-occurring pressure gradients,blood flows from the higher pressure femoral artery to the lowerpressure coronary sinus, inducing at least some retrograde flow throughthe venous vasculature. An occlusion balloon disposed on the outlet endof the delivery catheter may be selectively actuated to occlude outflowthrough the coronary sinus ostium.

The delivery catheter and optionally, the arterial line, includes aninjection port to permit autologous material to be added to the bloodinfused into the coronary sinus. Because outflow through the coronarysinus ostium is occluded, blood perfused into the coronary sinus willmigrate through the thebesian system, causing stem cells to embed in themyocardium and promote tissue regeneration. After a suitable period haselapsed, the inlet end of the delivery catheter may be uncoupled fromthe arterial line to permit any residual material to be aspirated fromthe coronary sinus via the delivery catheter. The occlusion balloon thenis deflated and the outlet end of the delivery catheter removed from thecoronary sinus.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the present invention willbe apparent upon consideration of the following detailed description,taken in conjunction with the accompanying drawings, in which likereference characters refer to like parts throughout, and in which:

FIG. 1 is a partial perspective view of a human heart illustrating thecoronary arteries;

FIG. 2 is a partial perspective view of a human heart illustrating thecardiac veins;

FIG. 3 is a sectional view of the myocardium, showing certain componentsof the cardiac venous system;

FIG. 4 is a side view of apparatus of the present invention, including adelivery catheter and a flow control catheter;

FIGS. 5A and 5B are, respectively, a cross-sectional view taken alongline 5B-5B of the delivery catheter of FIG. 4 and a cross-sectional viewtaken along line 5B-5B of the flow control catheter of FIG. 4;

FIG. 6 is a sectional view of a human heart showing the placement of theapparatus of the present invention;

FIG. 7 is a perspective view of an alternative embodiment of theapparatus of the present invention;

FIG. 8 is a sectional view of the delivery catheter of FIG. 7 takenalong view line 8-8 of FIG. 7;

FIG. 9 is a side-sectional view of a pressure-driven pump of the presentinvention suitable for use with the apparatus of FIG. 7;

FIG. 10 is a schematic illustration showing deflection of the conicalmember of FIG. 9 responsive to the systolic pressure wave communicatedthrough the arterial line;

FIG. 11 is a side-sectional view of an alternative embodiment of thepressure-driven pump of FIG. 9; and

FIG. 12 is a side-sectional view of another alternative embodiment of apressure-driven pump of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 3 depict the coronary arterial and venous systems of a humanheart. In FIG. 1, the myocardium of heart 10 is nourished by leftcoronary artery 11 and right coronary artery 12. Left coronary artery 11comprises circumflex branch 13 and left anterior descending coronaryartery 14; right coronary artery 12 comprises descending posteriorbranch 15 and marginal branch 16. Left and right coronary arteries 11and 12 emanate from aorta 17.

Referring to FIG. 2, the cardiac venous system of heart 10 comprisescoronary sinus 20, which provides drainage for great cardiac vein 21,middle cardiac vein 22, and small cardiac vein 23. Deoxygenated bloodflowing into coronary sinus 20 exits via coronary sinus ostium 24 intothe right atrium. The venous system further includes anterior cardiacveins 25 that drain directly into the right atrium.

With respect to FIG. 3, myocardium 26 has a lattice of capillaries 27that drain deoxygenated blood into intramyocardial veins 28. Frommyocardial veins 28, a fraction of the blood drains into the cardiacveins via subepicardial veins 29, while the remainder passes throughThebesian veins 30 directly into the atrial and ventricular cavities.Approximately 70% of the deoxygenated blood is drained through thecoronary sinus, while the remaining 30% is drained in about equalproportions into the left and right atria and ventricles via thelymphatic system and Thebesian veins. When individual components of thevenous system (i.e., the coronary sinus, lymphatic system and Thebesianveins) are occluded, the flow redistributes itself through the remainingunoccluded channels. In addition, it has been observed that adequatedrainage of deoxygenated blood can be provided by the lymphatic systemand the Thebesian veins even when the coronary sinus is totallyoccluded.

The coronary arteries are formed of resilient tissue fibers thatwithstand the peak pressures typically generated in the left ventricleduring cardiac systole, generally up to about 114 mm Hg. By contrast,the tissue fibers of the cardiac veins are much less resilient thanthose of the coronary arterial system, with peak pressures in thecoronary sinus generally in a range of 6-10 mm Hg.

Referring now to FIGS. 4 and 5, apparatus constructed in accordance withthe principles of the present invention is described. Apparatus 35comprises delivery catheter 40 for injecting donor stem cells,endothelial progenitor cells and mediators of stem cell mobilization,migration and attachment or autologous material, into the myocardialvasculature and flow control catheter 50 for controlling the rate offlow of blood exiting the coronary sinus.

Delivery catheter 40 includes proximal end having inlet port 41 and adistal end including occlusion balloon 42 and outlet port 43. Deliverycatheter 40 further includes guide wire port 44, balloon inflation port45 and injection port 46. As shown in FIG. 6A, delivery catheter 40includes lumen 47, which couples inlet port 41, guide wire port 44 andinjection port 46 to outlet port 43. Lumen 48 couples inflation port 45to the interior of occlusion balloon 42. Inlet port 41 is configured tobe coupled to a blood pump; the distal end of delivery catheter 40includes atraumatic tip 49 that is configured facilitate insertion intoa coronary artery along guide wire 70. Injection port 46 may beconfigured to accept conventional syringe 74 to introduce a solutioncontaining stem cells or autologous material into blood passing throughlumen 47 of the delivery catheter, or alternatively may include a luerfitting that enables connection to an infusion pump.

Flow control catheter 50 includes a proximal end having guide wire inletport 51 and inflation port 52, and a distal end having occlusion balloon53 and guide wire outlet port 54. As shown in FIG. 5B, lumen 55 extendsbetween the guide wire inlet portion 51 and guide wire outlet port 54,while lumen 56 coupled inflation port 52 to the interior of occlusionballoon 53. Lumen 55 enables flow control catheter 50 to be advancedalong pre-placed guidewire 71 so that occlusion balloon 53 may bedisposed in a patient's coronary sinus to selectively occlude outflowthrough the coronary sinus ostium. Optional flow sensor 57, e.g., apiezoelectric ultrasound element, may be disposed on catheter 50proximal of balloon 53 to monitor the flow of blood passing through thecoronary sinus ostium into the vena cava.

Delivery catheter 40 and flow control catheter 50 are designed for usetogether to permit a solution containing autologous or donor stem cells,endothelial progenitor cells and mediators of stem cell mobilization,migration and attachment or autologous material including stem cells, tobe introduced into a patient's infarcted myocardium promptly after theblockage resulting from an acute MI is opened. In accordance with theprinciples of the present invention, flow control catheter slowsdrainage of blood through the coronary venous vasculature. In thismanner, stem cells or other autologous material injected from syringe 74into the artery of the infarcted tissue via delivery catheter 40 willhave a slower transit time through the tissue, with enhanced likelihoodthat the material will become imbedded in the effected tissue.

Alternatively, delivery catheter 40 may be used to enhance oxygenationof the myocardium before the coronary artery is opened. In this manner,the apparatus of the present invention may be deployed and utilized toreduce further myocardial injury and establish retrograde flow prior tothe introduction of biologic material into the target region.

More specifically, with reference to FIG. 6, a method of using catheters40 and 50 to treat myocardial infarction resulting from blockage-inducedacute ischemia is described. After a patient suffering from acute MIarrives at a hospital, angioplasty or other another appropriateinterventional procedure may be performed on an urgent basis using aballoon catheter inserted along guide wire 70 inserted into coronaryartery CA. Once the blockage in coronary artery CA has been located andremoved, the balloon catheter is withdrawn, and guide wire 70 is left inposition. Delivery catheter 35 then is advanced along guide wire 70until balloon 42 is disposed in coronary artery CA at a locationproximal of the infarcted tissue.

Guide wire 71 is inserted into the patient's coronary sinus CS via aroute through either superior vena cava SVC or inferior vena cava IVC.In FIG. 6, guide wire 71 illustratively is advanced through the axillaryand subclavian veins (not shown) and into right atrium RA via superiorvena cava SVC. Flow control catheter 50 is advanced along guide wire 71until balloon 53 is disposed just inside coronary sinus ostium O.Balloon 53 is inflated to occlude or partially occlude the coronarysinus ostium and create backpressure in the coronary venous vasculaturethat slows the drainage of blood through the myocardium. Balloon 53 maybe especially configured to be retained in the coronary sinus ostium,for example, by including a roughened exterior surface that enhancesadhesion to the wall of the coronary sinus ostium.

A solution containing autologous or donor stem cells, endothelialprogenitor cells and mediators of stem cell mobilization, migration andattachment or alternatively containing filtered autologous bone marrowaspirant, is then injected from syringe 74 into the artery via outletport 43 of delivery catheter 40. Catheters 40 and 50 may remain deployedfor a predetermined period of time to permit the injected material tobecome embedded in the infarcted tissue. Balloons 42 and 53 of therespective catheters 40 and 50 then may be deflated, and the cathetersremoved to permit normal antegrade flow to become re-established.

In this manner, passage of blood through the infarcted myocardium may besubstantially slowed or arrested, thereby increasing stem cell residencetime and enhancing uptake in the affected region. The degree ofocclusion provided by flow control catheter 50 may be adjusted tocontrol outflow of blood through the coronary sinus ostium, and flowcontrol catheter 50 may further include a flow sensor disposed on theexterior of the catheter 50 proximal of balloon 53, to monitor the rateof blood outflow through the partially occluded coronary sinus ostium.

Alternatively, in accordance with another aspect of the presentinvention, it may be desirable to maintain occlusion of the coronarysinus for a predetermined period of time, e.g., to permit uptake of thestem cells in the infarcted tissue, followed by aspiration of theinjected material from the artery. This may be accomplished, forexample, by drawing suction on port 41 of delivery catheter 40 whiledeflating balloon 53 of delivery catheter 50. In this manner, a reverseflow may be established in the coronary artery and connected venousvasculature. Any unembedded injectate accordingly may be aspirated fromthe coronary vasculature, thereby ensuring that the material does notembolize or otherwise escape into systemic circulation. Once asufficient quantity of blood has been aspirated, balloon 42 of deliverycatheter 40 may be deflated. Catheters 40 and 50 then may be removed,permitting normal antegrade flow to become reestablished.

Referring now to FIGS. 7 and 8, an alternative embodiment of apparatusconstructed in accordance with the principles of the present inventionis described. As described herein below, apparatus 75 combines certainof the features of catheters 40 and 50, but instead employs retrogradeflow through the coronary vasculature to embed stem cells endothelialprogenitor cells and mediators of stem cell mobilization, migration andattachment in an infarcted region of tissue, rather than antegrade flowas in the system of FIG. 4.

Apparatus 75 comprises delivery catheter 80 and arterial line 90.Delivery catheter 80 includes distal end 81, which is configured to beplaced in a patient's coronary sinus, and proximal end 82, whichincludes inlet port 83 to be coupled to arterial line 90. Arterial line90 includes arterial cannula 91 at distal end 92 that is configured tobe placed in a patient's femoral artery, and proximal end 93, whichincludes luer-type fitting 94 for coupling the proximal end of thearterial line to inlet port 83 of the delivery catheter. Arterial line90 further may include optional injection port 96, for purposesdescribed herein below.

Proximal end 82 of delivery catheter 80 further includes guide wireinsertion port 84, injection port 85 and balloon inflation port 86.Distal end 81 includes outlet port 81a and compliant balloon 87 that isconfigured to be inserted into, and partially or fully occlude, apatient's coronary sinus. Outlet port 81 a, inlet port 83, guide wireinsertion port 84 and injection port 85 all communicate with lumen 88 ofthe delivery catheter (see FIG. 8), while balloon inflation port 86communicates with the interior of balloon 87 via inflation lumen 89.

When apparatus 75 is emplaced in a patient, a positive pressure gradientwill be established between distal end 92 of arterial line 90 and distalend 81 of delivery catheter, thus causing retrograde flow through thevenous vasculature. This flow will in turn result in a greater portionof the blood draining through the Thebesian system, as describedhereinabove with respect to FIG. 3.

In accordance with this aspect of the present invention, syringe 96 iscoupled to injection port 85 to inject a solution containing autologousor donor stem cells into blood flowing through lumen 88. In this manner,the stem cells endothelial progenitor cells and mediators of stem cellmobilization, migration and attachment may be carried into the venousvasculature and then become embedded in the infarcted myocardium.Alternatively, an infusion pump may be substituted for syringe 96 toprovide a metered amount of stem cell endothelial progenitor cells andmediators of stem cell mobilization, migration and attachment injectateover a predetermined period of time.

As yet a further alternative, optional blood pump 97, e.g., aperistaltic pump, may be connected to inlet port 83 of delivery catheter80 and proximal end 93 of arterial line to assist in establishingretrograde flow through the coronary venous vasculature. In this case,pressure sensor 98, or a pressure sensing lumen, may be mounted ondistal end 81 distal of balloon 87 to measure the pressure in thecoronary sinus. If a pressure-sensing lumen is provided, it may becoupled via a side port of catheter 80 to an external transducer thatpermits pressure in the coronary sinus to be measured. Thus, forexample, a sudden drop in the observed pressure could indicate that theballoon had deflated or migrated out of the coronary sinus.

In either of the foregoing configurations, the output of the means formeasuring pressure in the coronary sinus may be used to control pump 97to reduce the risk of edema of the coronary veins. As a still furtheralternative, pump 97 may be substituted for arterial line 90 in itsentirety, with the blood supplied from blood bags filled with autologousor donor blood.

Operation of apparatus 75 of FIG. 7 to treat myocardial infarctionresulting from blockage-induced acute ischemia in accordance with theprinciples of the present invention is described. After a patientsuffering from acute MI arrives at a hospital, angioplasty or otheranother appropriate interventional procedure may be performed on anurgent basis using conventional methods. Once the blockage in thecoronary artery has been located and removed, arterial cannula 91 isplaced in a conveniently located artery, such as the femoral artery.Alternatively, the apparatus of FIG. 7 may be placed in the coronarysinus ostium prior to opening of the blockage to enhance perfusion ofthe myocardium while the blockage is located and removed, therebyreducing further myocardial injury.

In either of the foregoing cases, a guide wire is inserted into thepatient's coronary sinus via a route through either the superior venacava or inferior vena cava, for example, through the axillary andsubclavian veins and into right atrium via superior vena cava. Deliverycatheter 80 is advanced along the guide wire until balloon 87 isdisposed just inside the coronary sinus ostium. Balloon 87 is inflatedto occlude or partially occlude the coronary ostium and create abackpressure in the coronary venous vasculature that slows the drainageof blood through the venous vasculature. After the air is cleared fromlumen 88, e.g., by permitting backbleed through guide wire port 84,fitting 94 of arterial line 90 is coupled to inlet port 83 of deliverycatheter 80 to induce retrograde flow in the coronary venousvasculature. Due to naturally-occurring pressure gradients, blood flowsfrom the higher pressure femoral artery to the lower pressure coronarysinus, thereby inducing retrograde flow through the venous vasculature.

A solution containing autologous or donor stem cells, endothelialprogenitor cells or mediators of stem cell mobilization, migration andattachment or alternatively containing autologous bone marrow aspirant,is then injected from syringe 96 into the coronary veins via lumen 88and outlet port 81 a of delivery catheter 80. Delivery catheter 80 mayremain deployed for a predetermined period of time to permit theinjected material to become embedded in the infarcted tissue. Balloon 87then may be deflated, and the catheter removed to permit normalantegrade flow to become re-established through the coronary veins.

As for the preceding embodiment, balloon 87 of apparatus 75 of FIG. 7substantially slows or arrests the flow of blood through the infarctedmyocardium, thereby increasing stem cell, endothelial progenitor cellsor mediators of stem cell mobilization, migration and attachmentresidence time and enhancing uptake in the affected region. The degreeof occlusion provided by balloon 87 may be adjusted to control outflowof blood through the coronary sinus ostium, and distal end 81 of thedelivery catheter further may include a flow sensor disposed proximal ofballoon 87 to monitor the outflow rate.

Alternatively, it may be desirable to maintain occlusion of the coronarysinus for a predetermined period of time, e.g., to permit uptake of thestem cells in the infarcted tissue, followed by aspiration of theinjected material from the venous vasculature. This may be accomplished,for example, by uncoupling arterial line 90 from inlet port 83, and thendrawing suction on port 83 to induce antegrade flow through the venousvasculature. Any unembedded injectate accordingly may be aspirated fromthe coronary vasculature, thereby ensuring that the material does notembolize or otherwise escape into systemic circulation. Once asufficient quantity of blood has been aspirated, balloon 87 of deliverycatheter 80 may be deflated and catheter 80 may be removed.

Referring now to FIGS. 9, a pressure-driven pump suitable for use withapparatus 75 of the present invention is described. Pump 100 may becoupled to apparatus 75 between fitting 94 of the arterial line andinlet port 83 of delivery catheter 80. In accordance with the principlesof the present invention, pump 100 is configured to store pressureenergy during systole, and release that pressure energy during diastole.In particular, because during systole the heart muscle contracts, it ishypothesized that it may be difficult to inject stem-cell laden blood,endothelial progenitor cells or mediators of stem cell mobilization,migration and attachment into the venous vasculature during that portionof the cardiac cycle. Pump 100 therefore stores kinetic energy from thepressure wave provided from the blood passing through arterial line 90,and releases that energy during diastole, when the pressure differentialis expected to be more favorable to retrograde flow through the cardiacveins. As will of course be understood, pump 100 may be directlysubstituted for pump 96 of FIG. 7.

In FIG. 9, pump 100 includes rigid housing 101 having inlet 102 andoutlet 103. Filter element 104 is slidably disposed in housing 101through leak-proof slot 105. Elastomeric conical member 106 is disposedin fluid communication between inlet 102 and outlet 103, and includeswall 106 having a graded thickness over its length that varies betweenT₁ and T₂, with T₁ being the thinnest portion. The thickness of the wallis selected so that wall deflects outward in response to predeterminedinternal pressures and may do so in a series of discrete steps, e.g., at50, 80, 110, 160 and 200 mm Hg.

Space 107 within housing 101 surrounding conical member 106 may beevacuated, or alternatively, may include vents that permit conicalmember to deflect without a corresponding pressure increase in the airin space 107. In a still further alternative embodiment, space 107 maybe pressurized to a desired pressure using a compressible gas, such asair. In this case, the pressure in space 107 may be selected or adjustedon a patient-by-patient basis to maximize efficiency of pump 100.One-way valve 108, which may be a conventional flap or duck-bill valve,opens during systole and closes during diastole so that conical member106 remains pressurized during diastole.

Pump 100 operates as follows: During systole, blood received fromarterial line 90 enters the interior of conical member 106 via inlet 102and one-way valve 108. Because the myocardium contracts during systole,the pressure differential between inlet 102 and outlet 103 may berelatively small. However, in accordance with one aspect of the presentinvention, conical member 106 will begin deflecting outward starting atthe thinnest region T₁. As the pressure continues to rise within theinterior of conical member 106, additional regions deflect outward,thereby storing the kinetic energy of the pressure wave into potentialenergy corresponding to displacement of the wall of conical member 106.FIG. 10 is a schematic illustration of exemplary deflection of regionsof conical member 106 at times t₁ through t₄ and corresponding pressuresP₁ through P₄ during systole.

Once the diastolic portion of the cardiac cycle begins, pressure in thevenous vasculature is expected to drop off quickly. This in turn permitsthe potential energy stored in deflection of conical member 106 to betransformed into kinetic energy in the form of a delayed pressure wave,which drives blood from the interior of conical member 106 throughoutlet 103 and into the venous vasculature. Over several cardiac cycles,the pressure wave provided by pump 100 assists in establishing andmaintaining retrograde in the cardiac venous vasculature. As will beseen, pump 100 therefore serves as a mechanism to temporally shift thesystolic pressure wave encountered in the femoral artery to thediastolic portion of the myocardial cycle.

Filter 104 of pump 100 preferably comprises a pre-selected pore size,such as 200 microns, and serves to trap emboli or clots carried in theblood received from arterial line 90. In addition, if optional injectionport 95 of arterial line 90 is used to inject the solution containingthe stem cells endothelial progenitor cells or mediators of stem cellmobilization, migration and attachment into the blood transfused intothe coronary venous vasculature, filter 104 may be used to trap unwantedparticles from entering the patient's circulation.

For example, typically there will be insufficient time to cultureautologous stem cells prior to onset of an acute myocardial infarction,since such events are by definition unpredictable. In accordance withone aspect of the present invention, it is contemplated that after theblockage is removed from the effected coronary artery, raw bone marrowmay be aspirated from the patient's iliac crest. Apparatus 75 is thenpositioned as described above, and the bone marrow aspirant may bedirectly injected into the blood flowing through arterial line 90 usinginjection port 95. Raw bone marrow aspirant typically will contain somematerial that should not be injected into the vasculature (fatparticles, bone stromal material, etc.). Filter 104 may be configured tofilter out these unwanted components of the bone marrow, whilepermitting the stem cells endothelial progenitor cells and mediators ofstem cell mobilization, migration and attachment to be carried into, andbecome embedded in, the infarcted portion of the myocardium via deliverycatheter 80.

With respect to FIG. 11, an alternative embodiment of a pump forshifting a pressure wave from the systolic portion to diastolic portionof the cardiac cycle is described. Pump 110 is similar in constructionto pump 100 of FIG. 9; like-primed numbers indicate correspondingcomponents of the embodiment of FIG. 9. In addition, pump 110 includesstepped inner surface 111 that controls deflection of conical member. Inparticular, stepped inner surface 111 of housing 101′ limits deflectionof a corresponding region of conical member 106′, and may enhancemanufacturability of the pump.

In yet a further alternative embodiment depicted in FIG. 12, pump 120includes a rigid housing comprising telescoping concentric tubes 121 and122. Tube 121 includes inlet 123; tube 122 includes outlet 124. Filter125 is replaceable inserted through leak-proof slot 126. Elastomericmember 127 defines interior space 128 disposed in fluid communicationwith inlet 123 and outlet 124. Elastomeric member 127 is configured toextend axially responsive to pressure buildup within space 128 duringsystole, and returns that energy to the blood in the form of a pressurewave during diastole. One-way valve 129 permits inflow into elastomericmember 127 during systole and closes during diastole to retainelastomeric member 127 under pressure. Operation of apparatus of pump120 is similar to that described above for pump 100, except that theelastomeric member 127 undergoes longitudinal deflection responsive topressure build-up rather than radial deflections in the embodiment ofFIGS. 9 and 11.

Although preferred illustrative embodiments of the present invention aredescribed above, it will be evident to one skilled in the art thatvarious changes and modifications may be made without departing from theinvention. It is intended in the appended claims to cover all suchchanges and modifications that fall within the true spirit and scope ofthe invention.

1. Apparatus for treating acute myocardial infarction by embedding stemcells, endothelial progenitor cells or mediators of stem cellmobilization, migration and attachment, into an infarcted region ofmyocardium, comprising: a delivery catheter for injecting a solutioncontaining stem cells into the infarcted region of myocardium, thedelivery system having a proximal end including an inlet port and aninjection port, a distal end having an outlet port, and a lumen in fluidcommunication with the inlet port and the outlet port; means forpartially or fully occluding outflow through a patient's coronary sinus;and means for inducing a pressure differential between the inlet portand the outlet port of the delivery catheter.
 2. The apparatus of claim1, wherein the means for partially or fully occluding outflow through apatient's coronary sinus comprises a flow control catheter having adistal end configured to be inserted into the coronary sinus.
 3. Theapparatus of claim 2, wherein the means for partially or fully occludingoutflow through a patient's coronary sinus comprises a balloon disposedon the distal end of the flow control catheter.
 4. The apparatus ofclaim 2, wherein the flow control catheter further comprises a sensordisposed on the distal end to monitor outflow through the coronarysinus.
 5. The apparatus of claim 2, wherein the delivery catheter isconfigured to be inserted via a femoral or brachial artery and guidedinto a coronary artery.
 6. The apparatus of claim 1, wherein thedelivery catheter further comprises: an occlusion balloon disposed onthe distal end proximal of the outlet port; an inflation port disposednear the proximal end; and an inflation lumen providing fluidcommunication between an interior of the occlusion balloon and theinflation port.
 7. The apparatus of claim 1, wherein the means forinducing a pressure differential between the inlet port and the outletport of the delivery catheter comprises a blood pump coupled to theinlet port of the delivery catheter.
 8. The apparatus of claim 1,further comprising a guide wire port.
 9. The apparatus of claim 1,further comprising a syringe coupled to the injection port fordelivering a solution containing stem cells, endothelial progenitorcells or mediators of stem cell mobilization, migration and attachment,into blood flowing through the delivery catheter.
 10. The apparatus ofclaim 1, wherein the means for partially or fully occluding outflowthrough a patient's coronary sinus comprises a balloon disposed on thedistal end of the delivery catheter.
 11. The apparatus of claim 2,wherein the flow control catheter further comprises means for sensingpressure in the coronary sinus.
 12. The apparatus of claim 2, whereinthe delivery catheter is configured to be inserted via a femoral veinand guided into a coronary sinus.
 13. The apparatus of claim 12, whereinthe delivery catheter further comprises a guide wire port thatcommunicates with the lumen.
 14. The apparatus of claim 12, furthercomprising a syringe coupled to the injection port for delivering asolution containing stem cells, endothelial progenitor cells ormediators of stem cell mobilization, migration and attachment, intoblood flowing through the delivery catheter.
 15. The apparatus of claim12, wherein the means for inducing a pressure differential between theinlet port and the outlet port of the delivery catheter comprises anarterial line coupled to the inlet port of the delivery catheter. 16.The apparatus of claim 15, further comprising a pump coupled between theinlet port of the delivery catheter and the arterial line.
 17. Theapparatus of claim 16, wherein the pump stores energy deposited by apressure wave during systole and releases the energy during diastole tofacilitate induction of retrograde flow in the coronary venousvasculature.
 18. The apparatus of claim 17 wherein the pump comprises: ahousing having an inlet and an outlet; a one-way valve coupled to theinlet; and an elastomeric member disposed within the housing in fluidcommunication with the inlet and the outlet, the elastomeric memberconfigured to undergo dimensional change that converts pressure waveenergy into potential energy during systole.
 19. The apparatus of claim18, wherein the dimensional change comprises radial deflection of theelastomeric member.
 20. The apparatus of claim 18, wherein thedimensional change comprises longitudinal deflection of the elastomericmember.
 21. A method of treating an infarcted region of a patient'smyocardium following an acute myocardial infarction, comprising: openinga blockage in a patient's coronary artery to relieve myocardialischemia; deploying a delivery catheter in a patient's coronary vessel;delivering a solution containing stem cells, endothelial progenitorcells or mediators of stem cell mobilization, migration and attachment,into the coronary vessel via the delivery catheter; and partially orfully occluding blood flow through a patient's coronary ostium tocontrol a rate of blood flow through the infarcted region to facilitateretention of the stem cells in the infarcted region.
 22. The method ofclaim 21, wherein deploying the delivery catheter in the patient'scoronary vessel comprises deploying the delivery catheter in thepatient's coronary vessel the coronary artery in which the blockage wasopened.
 23. The method of claim 22, further comprising providing a flowcontrol catheter, wherein partially or fully occluding blood flowthrough a patient's coronary sinus ostium comprises deploying the flowcontrol catheter in the patient's coronary sinus.
 24. The method ofclaim 23, wherein the flow control catheter comprises a distal endincluding an occlusion balloon, wherein partially or fully occludingblood flow through a patient's coronary sinus ostium comprises inflatingthe occlusion balloon.
 25. The method of claim 22, wherein the deliverycatheter further comprises a balloon disposed adjacent to an outlet endof the delivery catheter, the method further comprising deploying theballoon.
 26. The method of claim 24, further comprising, after apredetermined period after delivery of the solution containing stemcells, endothelial progenitor cells or mediators of stem cellmobilization, migration and attachment into the coronary vessel,deflating the occlusion balloon to allow blood within the coronary sinusto be aspirated through the delivery catheter.
 27. The method of claim22 further comprising monitoring a rate of blood outflow through thecoronary sinus ostium.
 28. The method of claim 21, wherein deploying thedelivery catheter in the patient's coronary vessel comprises deployingthe delivery catheter in the patient's coronary sinus.
 29. The method ofclaim 28, wherein the delivery catheter comprises an occlusion balloondisposed on an outlet end of the delivery catheter, wherein partially orfully occluding blood flow through a patient's coronary sinus ostiumcomprises deploying the occlusion balloon.
 30. The method of claim 28,wherein delivering a solution containing stem cells, endothelialprogenitor cells or mediators of stem cell mobilization, migration andattachment into the coronary vessel via the delivery catheter comprises:providing an arterial line; placing the arterial line a patient'sbrachial, radial or femoral artery; coupling the arterial line to aninlet end of the delivery catheter; communicating naturally-occurringpressure gradients through the arterial line and the delivery catheterto induce retrograde flow in the patient's coronary venous vasculature;and injecting the solution containing stem cells, endothelial progenitorcells or mediators of stem cell mobilization, migration and attachmentinto blood transfused through the arterial line and the deliverycatheter into the patient's coronary venous vasculature.
 31. The methodof claim 30 further comprising coupling a pump between the arterial lineand the delivery catheter, further comprising shifting a pressure wavecommunicated through the arterial line during systole to a pressure wavecommunicated through the delivery catheter during diastole.
 32. Themethod of claim 28, further comprising, after a predetermined periodafter delivery of the solution containing stem cells, endothelialprogenitor cells or mediators of stem cell mobilization, migration andattachment into the coronary vessel, aspirating blood from within thecoronary sinus.
 33. The method of claim 28 further comprising monitoringa pressure in the coronary sinus.